1. Field of Technology
This invention relates generally to the field of catalysis. More specifically, the invention relates to methods of using metal oxide materials for catalytic upgrading of chemical species.
2. Description of Related Art
The general strategy of cyclic catalytic conversion and chemical looping has been reported previously in the literature. The chemical looping partial oxidation of hydrocarbons is taught by Zeng, et al.19-21 The use of iron oxides in coal gasification in a chemical looping system has been previously reported for converting carbon monoxide in synthesis gas to CO2 (for subsequent decarbonation).25,26 Additionally, its use in a thermal looping cycle in the same art was evident: thermal energy deposited into the oxygen carrier upon exposure to fuel could then be released upon air oxidation. A coal gasification system (by GE Global Research) employing transition metal (including iron) oxides27 has been reported. Alstom Power has also reported a gasification system which utilizes calcium oxide.28 
The use of metal oxide materials for chemical looping combustion of natural gas and methane has appeared in the literature frequently.1-16 The use of metal oxide materials for cyclic partial oxidation of gaseous hydrocarbons has appeared much less frequently in the literature. Nevertheless, in one instance NiO supported on Al2O3 was investigated in the chemical looping reforming of methane.17 The process reported by Lyon uses a packed bed reactor which is alternately exposed to natural gas and air.23 The packing is a catalyst comprised of NiO, Fe2O3, MnO, CuO, CoO, CdO, ZnO or mixtures thereof. Lyon also reports a process for heat transfer by unmixed combustion.24 The process utilizes a reactor packed with nickel oxide, copper oxide, cobalt oxide, silver oxide, tungsten oxide, manganese oxide, or molybdenum oxide which is exposed to a reducing gas, converting the metal oxides to the corresponding metals. The metals are converted back to the metal oxides upon exposure to an oxidizing gas. Additionally, strontium sulfate or barium sulfate can be employed, which, when contacted with reducing gas, are converted to the corresponding sulfides. In this manner, heat can be transferred to the endothermic process (reduction of oxidizing gas).
The chemical looping reforming of liquid fuels has not been reported extensively. The only such prior art is due to Kunii and Kunugi who report a continuous process for catalytic gasification of heavy hydrocarbon oils,22 and that assigned to BOC who reported the use of perovskitic metal oxides in the cyclic partial oxidation of liquid fuel.
The use of metal oxide materials in separating oxygen from air is a novel process for providing oxygen for various processes. However, its use has been reported in the literature. Specifically, the use of perovskite metal oxides in the cyclic autothermal recovery (CAR) process utilizes the metal oxides as oxygen storage materials to provide oxygen to a number of processes.18 
There is continuing interest in oxygen-carrying materials for use in a variety of processes.